How Cow's make milk
Describe the milk let down response in dairy cows.
Milk is initially secreted into small sacs within the mammary gland called alveoli, it is from here that it is ejected for consumption or harvesting. Anatomy of a teat Mammary alveoli are surrounded by smooth muscle cells which are a prominent target cell for oxytocin. Oxytocin stimulates contraction of these cells, causing milk to be ejected into the ducts and cisterns above the teat. Oxytocin is released after the cow receives an appropriate stimulus - this can be visual, aural or physical, and should be predictable and consistent at every milking. Handling/massage of the teats for at least 15sec is a strong stimulus, but cows can also learn to let down through the association of the dairy environment to the milking process. The pressure of milk being forced into the ducts/cistern and down towards the teat causes the teat to swell with milk and become ‘plump’. It takes 60 - 90 seconds for teats to become plump after let down has been initiated. Cows with well-filled udders require a shorter period of stimulation to elicit a milk let down response than cows with less-filled udders. The action of oxytocin is essential for emptying of the udder during milking. As much as 80% of a cow’s milk is unavailable if this oxytocin release is insufficient or does not occur. Its let down action lasts for about 5 minutes and is strongest for the first 3 minutes of milking. It is important to get the cups attached quickly after let down has started to make full use of the increased udder pressure that occurs. |
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Describe the composition of cow’s milk.
Milk CompositionThe Milk Composition section describes the chemical and physical properties and effects of pasteurization on the compounds in milk. A brief overview of the variation in milk composition is provided below as an introduction to this section. Topics covered are:
Unless otherwise stated, the information presented in this website refers to cow's milk. In general, the gross composition of cow's milk in the U.S. is 87.7% water, 4.9% lactose (carbohydrate), 3.4% fat, 3.3% protein, and 0.7% minerals (referred to as ash). Milk composition varies depending on the species (cow, goat, sheep), breed (Holstein, Jersey), the animal's feed, and the stage of lactation. Although there are minor variations in milk composition, the milk from different cows is stored together in bulk tanks and provides a relatively consistent composition of milk year round |